Cylinder assembly for a mini air compressor

ABSTRACT

A cylinder assembly for a mini air compressor includes a cylinder, a discharge check valve, a piston, a supply check valve and a piston rod. The cylinder has two open ends, and the piston with an open end and a closed end is slidably mounted in the cylinder. A supply check valve is mounted on the closed end of the piston. A discharge check valve is adapted to mount on and seal one end of the cylinder. At least one of the supply check valve and the discharge check valve has with a flexible, resilient disk. Two check valves are configured such that only one valve opens at a time when the piston slides in the cylinder.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cylinder assembly for a miniair compressor and more particularly to a cylinder assembly for a miniair compressor with at least one simplified check valve that uses aresilient disk to open and close the valve.

[0003] 2. Description of Related Art

[0004] Air compressors increase the pressure of air for application inother devices or systems. A reciprocating air compressor has at leastone cylinder assembly to compress the air. With reference to FIG. 5, thecylinder assembly (70) includes a piston rod (71), a cylinder (72), apiston (73), a supply check valve (74) and a discharge check valve (75).The cylinder (72) has an open end and a closed end. The piston (73) iscylindrical with two ends, one open and one closed, pivotally attachedto the piston rod (71) near the open end and is slidably mounted in thecylinder (72) with the closed end facing the closed end of the cylinder(72). The supply check valve (74) is mounted in the closed end of thepiston (73). The discharge check valve (75) is mounted in the closed endof the cylinder (72). The piston rod (71) drives the piston (73), andthe piston (73) moves reciprocally in the cylinder (72). Thereciprocating motion of the piston (73) draws air into the cylinder (72)through the supply check valve (74) during one stroke and compresses theair when the piston (73) slides toward the discharge check valve (75).The compressed air passes through the discharge check valve (75) and isaccumulated in a storage container such as an air tank.

[0005] A conventional discharge check valve (75) is composed of a valveport (751), a valve spring (752) and a valve disk (753). Air passes outof the cylinder (72) and into the discharge check valve (75) through thevalve port (751), and the valve disk (753) selectively opens the valveport (751) to allow air to flow into the discharge check valve (75)only. The valve spring (752) presses the valve disk (753) against thevalve port (751) to keep the discharge check valve (75) normally closedunless pressure is applied to the face of the valve disk (753) toovercome the force of the valve spring (752). When the piston (73) istraveling away from the discharge check valve (75), the supply checkvalve (74) is open and the discharge check valve (75) is closed.

[0006] This mechanical structure has the following shortcomings:

[0007] Expensive and complex:

[0008] Because this kind of check valve has numerous parts several ofwhich must be machined to ensure a tight fit, the valve is expensive,and the structure is more complex than necessary especially for lowpressure applications. The valve disk (753) has a special shapeincluding a device around which the valve spring (752) is mounted andthe surface that abuts and closes the valve port (751). The precisionrequired to is make the valve keeps cost of the cylinder assembly frombeing reduced significantly.

[0009] Efficiency issue:

[0010] The valve spring (752) presses the valve disk (753) against andcloses the valve port (751). Each cycle of the piston (73) compressesthe valve spring (752), which causes the valve spring (752) to lose itsresilience and reduce the elastic force pressing the valve disk (753)closed. Consequently, air will escape back into the cylinder (72) beforethe valve port (751) is closed completely, and the compressionefficiency of the cylinder assembly is reduced.

[0011] To overcome the shortcomings, the present invention provides animproved cylinder assembly to mitigate and/or obviate the aforementionedproblems.

SUMMARY OF THE INVENTION

[0012] The main objective of the invention is to provide a simplifiedcylinder assembly for a mini air compressor. The cylinder assemblyincludes a cylinder with two open ends, a discharge check valve ismounted in one open end and a strongback is mounted over the dischargecheck valve. A piston with an open end and a closed end is mounted inthe cylinder through the other open end of the cylinder. The open end ofthe piston faces the open end of the cylinder, and the closed end facesthe discharge check valve. A supply check valve is mounted over supplyports in the closed end of the piston, and a piston rod is connected tothe piston through the open end of the piston. Besides the supply portsformed in the closed end of the piston, at l least one discharge port isformed in the discharge check valve. At least one of the supply checkvalve and the discharge check valve has a resilient disk attached to thevalve to cover the corresponding valve port. The two check valves areconfigured so only one valve opens at a time when the piston slides inthe cylinder. Accordingly, the structure of the cylinder is simplified,and the cost for manufacturing the cylinder is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is an exploded perspective view of an air compressor withtwo cylinder assemblies in accordance with the present invention;

[0014]FIG. 2 is an exploded perspective view of a cylinder assembly inFIG. 1;

[0015]FIG. 3 is an operational side plan view in partial section of thecylinder assembly in FIG. 2;

[0016]FIG. 4 is an operational side plan view in partial section of thecylinder assembly in FIG. 2; and

[0017]FIG. 5 is a side plan view in partial section of a conventionalcylinder assembly of an air compressor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0018] With reference to FIG. 1, a mini air compressor comprises achassis (10), a motor (11), a gearbox (12), a driven shaft (13), aneccentric drive wheel (14) and two cylinder assemblies (20). The chassis(10) has two sides. The motor (11) has a drive shaft and is attached toone side of the chassis (10). The drive shaft extends through thechassis (10). The gearbox (12) with an enclosed gear set (122) isattached to the side of the chassis (10) opposite to the motor (11). Thegear set (122) is connected to the drive shaft of the motor (11). Thedriven shaft (13) has two ends and passes through the chassis (10) withone end on each side of the chassis (10). One end of the driven shaft(13) is connected to the gear set (122). The eccentric drive wheel (14)is connected to the other end of the driven shaft (13). The cylinderassemblies (20) are connected to the eccentric drive wheel (14) and aremounted on the chassis (10).

[0019] To operate the mini-air compressor, the motor (11) generates thepower, and the drive shaft drives the gear set (122) in the gearbox(12). The gearbox (12) adjusts the power and outputs the power to thedriven shaft (13). The driven shaft (13) rotates the eccentric drivewheel (14), and the eccentric drive wheel (14) drives the cylinderassemblies (20).

[0020] With further reference to FIGS. 2 and 3, the cylinder assembly(20) in accordance with the present invention comprises a cylinder (21),a piston (22), a piston rod (23), a supply check valve (24), a dischargecheck valve (25) and a strongback (26). The cylinder (21) has two openends (212, 214). The piston (22) is cylindrical with an inside andoutside and has an open end (222) and a closed end (224). The piston(22) is slidably mounted in the cylinder (21) through one open end (214)of the cylinder (21) with the open end (222) of the piston (22) facingthe outside of the cylinder (21). The piston rod (23) is pivotallyattached to the inside of the piston (22) through the open end (222).The supply check valve (24) is mounted on the closed end (224) of thepiston (22) facing the inside of the cylinder (21). The discharge checkvalve (25) is mounted on the open end (212) of the cylinder (21)opposite to the end through which the piston (22) is mounted. Thestrongback (26) is mounted over and holds the discharge check valve (25)on the open end (212) of the cylinder (21). A discharge fitting (262) isformed on the strongback (26).

[0021] The supply check valve (24) and the discharge check valve (25)have the same basic structure with minor variations. The supply checkvalve (24) comprises supply ports (241), a disk stub (242) and aresilient disk (243). The supply ports (241) are defined through theclosed end (224) of the piston (22). The disk stub (242) is a shortshaft with a slightly enlarged head (244), is formed on the closed end(224) of the piston (22) and extends into the cylinder (21). Theresilient disk (243) is a circular piece of flexible, resilient materialwith a hole in the center to mount the resilient disk (243) on the diskstub (242) to cover the supply ports (241). The discharge check valve(25) comprises a body (251), discharge ports (252), a disk stub (253)and a resilient disk (254). The body (251) has an inside end and anoutside end and is adapted to be mounted on and seal one end (212) ofthe cylinder (21). The discharge ports (252) are formed through the bodyto communicate with the inside of the cylinder (21). The disk stub (253)is a short shaft with a slightly enlarged head (255), is formed on theoutside end of the body (251) and extends away from the cylinder (21)toward the strongback (26). The resilient disk (254) is a circular pieceof flexible, resilient material with a hole in the center to mount theresilient disk (243) on the disk stub (253) to cover the discharge ports(252).

[0022] With reference to FIGS. 3 and 4, the cylinder assembly operatesby sliding the piston (22) in and out of the cylinder (21) to generate acompression stroke (sliding in) and a suction stroke (sliding out). Whenthe piston (22) slides out of the cylinder (21), the movement generatesa lower pressure in the cylinder (21) between the closed end (224) ofthe piston (22) and the discharge check valve (25) than a relativelyhigher ambient air pressure. The relatively higher ambient air pressurepresses the resilient disk (254) of the discharge check valve (25)against the body (251), which seals the discharge ports (252). Thiscloses the discharge check valve (25). Simultaneously, the relativelyhigher ambient air pressure presses the resilient disk (243) of thesupply check valve (24) away from the supply ports (241), which allowsair to flow into the cylinder (21) through the supply ports (241).

[0023] With reference to FIG. 4, when the piston (22) reverses directionand slides into the cylinder (21) toward the discharge check valve (25),the air in the cylinder between the piston (22) and the discharge checkvalve (25) is compressed such that the pressure of the air in thecylinder (21) is relatively higher than the ambient air pressure. Therelatively higher air pressure in the cylinder (21) pushes the resilientdisk (243) of the supply check valve (24) against and seals the supplyports (241). The relatively higher air pressure in the cylinder (21)pushes the resilient disk (254) away from the discharge ports (252) andthe compressed air flows through the discharge fitting to a means tostore or use the compressed air.

[0024] The invention simplifies the cylinder assembly and uses aflexible, resilient disk (243, 254) to cause the check valves (24, 25)to open and close in the cylinder (21). There is no problem aboutelastic fatigue or a machined shape of the valve disk. The flexible,resilient disk (243, 254) is simpler and cheaper than the machined valvedisk. The cylinder assembly is simpler, cheaper and more efficient. Inaddition, one of the simplified check valves can be instead of adifferent type of check valve such as the conventional check valve asshown in FIG. 5. The cylinder with a simplified check valve inaccordance with the present invention and a conventional check valve canalso achieve an effect of simplifying the structure of the cylinder.

[0025] Even though numerous characteristics and advantages of thepresent invention have been set forth in the foregoing description, itwill be obvious to those skilled in the art that various modificationsmay be made without departing from what is intended to be limited solelyby the appended claims.

What is claimed is:
 1. A cylinder assembly for a mini air compressorcomprising: a cylinder with a first and a second open ends; a dischargecheck valve with a body mounted on the first open end of the cylinderand at least one discharge port defined through the body of thedischarge check valve; a strongback mounted over and holding thedischarge check valve on the first open end of the cylinder; acylindrical piston with an inside and an outside, an open end and aclosed end slidably mounted in the cylinder through the second open endof the cylinder with the open end of the piston facing an outside of thecylinder; a piston rod pivotally attached to the inside of the pistonthrough the open end of the piston; and a supply check valve mounted onthe closed end of the piston facing an inside of the cylinder and atleast one supply port defined through the closed end of the piston,wherein at least one of the discharge and supply check valves has a diskstub with a short shaft and a slightly enlarged head formed on the valveand a resilient disk mounted on said disk stub and corresponding to theat least one port in the valve to cover said corresponding at least oneport.
 2. The cylinder assembly for a mini air compressor as claimed inclaim 1, wherein the supply valve has a disk stub formed on the closedend of said piston and extends toward the discharge check valve and aresilient disk mounted on said disk stub to cover said supply ports toallow said supply check valve to open toward said discharge check valve.3. The cylinder assembly for a mini air compressor as claimed in claim1, wherein the discharge valve has a disk stub facing said strongbackand formed on the body of said discharge check valve and a resilientdisk mounted on said disk stub to cover said discharge ports to allowthe discharge check valve to open toward said strongback.
 4. Thecylinder assembly for a mini air compressor as claimed in claim 1,wherein a discharge fitting is formed on the strongback.